Coded caching is a technique that generalizes conventional caching and promises significant reductions in traffic over caching networks. However, the basic coded caching scheme requires that each file hosted in the server be partitioned into a large number (i.e., the subpacketization level) of non-overlapping subfiles. From a practical perspective, this is problematic as it means that prior schemes are only applicable when the size of the files is extremely large. In this work, we propose coded caching schemes based on combinatorial structures called resolvable designs. These structures can be obtained in a natural manner from linear block codes whose generator matrices possess certain rank properties. We obtain several schemes with subpacketization levels substantially lower than the basic scheme at the cost of an increased rate. Depending on the system parameters, our approach allows us to operate at various points on the subpacketization level vs. rate tradeoff.

A novel microplasma molecular emission spectrometer based on an atmospheric pressure dielectric barrier discharge (DBD) is described and further used as a promising multichannel GC detector for halohydrocarbons. The plasma is generated in a DBD device consisting of an outer electrode (1.2 mm in diameter) and an inner electrode (1.7 mm in diameter) within a small quartz tube (3.0 mm i.d. × 5.0 mm o.d. × 50 mm), wherein analyte molecules are excited by the microplasma to generate molecular emission. Therefore, the analytes are selectively and simultaneously detected with a portable charge-coupled device (CCD) via multichannel detection of their specific emission lines. The performance of this method was evaluated by separation and detection of a model mixture of chlorinated hydrocarbons (CHCl(3) and CCl(4)), brominated hydrocarbons (CH(2)Br(2) and CH(2)BrCH(2)Br), and iodinated hydrocarbons (CH(3)I and (CH(3))(2)CHI) undergoing GC with the new detector. The completely resolved identification of the tested compounds was achieved by taking advantages of both chromatographic and spectral resolution. Under the optimized conditions with the CCD spectrometer set at 258, 292, and 342 nm channels for determination of chlorinated hydrocarbons, brominated hydrocarbons, and iodinated hydrocarbons, respectively, this detector with direct injection provided detection limits of 0.07, 0.06, 0.3, 0.04, 0.05, and 0.02 μg mL(-1) for CCl(4), CHCl(3), CH(2)Cl(2), CH(3)I, CH(3)CH(2)I, and (CH(3))(2)CHI, respectively.

While copper is an essential trace element in biology, pollution of groundwater from copper has become a threat to all living organisms. Cellular mechanisms underlying copper toxicity, however, are still not fully understood. Previous studies have shown that iron-sulfur proteins are among the primary targets of copper toxicity in Escherichia coli under aerobic conditions. Here, we report that, under anaerobic conditions, iron-sulfur proteins in E. coli cells are even more susceptible to copper in medium. Whereas addition of 0.2 mM copper(II) chloride to LB (Luria-Bertani) medium has very little or no effect on iron-sulfur proteins in wild-type E. coli cells under aerobic conditions, the same copper treatment largely inactivates iron-sulfur proteins by blocking iron-sulfur cluster biogenesis in the cells under anaerobic conditions. Importantly, proteins that do not have iron-sulfur clusters (e.g., fumarase C and cysteine desulfurase) in E. coli cells are not significantly affected by copper treatment under aerobic or anaerobic conditions, indicating that copper may specifically target iron-sulfur proteins in cells. Additional studies revealed that E. coli cells accumulate more intracellular copper under anaerobic conditions than under aerobic conditions and that the elevated copper content binds to the iron-sulfur cluster assembly proteins IscU and IscA, which effectively inhibits iron-sulfur cluster biogenesis. The results suggest that the copper-mediated inhibition of iron-sulfur proteins does not require oxygen and that iron-sulfur cluster biogenesis is the primary target of anaerobic copper toxicity in cells.IMPORTANCE Copper contamination in groundwater has become a threat to all living organisms. However, cellular mechanisms underlying copper toxicity have not been fully understood up to now. The work described here reveals that iron-sulfur proteins in Escherichia coli cells are much more susceptible to copper in medium under anaerobic conditions than they are under aerobic conditions. Under anaerobic conditions, E. coli cells accumulate excess intracellular copper, which specifically targets iron-sulfur proteins by blocking iron-sulfur cluster biogenesis. Since iron-sulfur proteins are involved in diverse and vital physiological processes, inhibition of ironsulfur cluster biogenesis by copper disrupts multiple cellular functions and ultimately inhibits cell growth. The results from this study illustrate a new interplay between intracellular copper toxicity and iron-sulfur cluster biogenesis in bacterial cells under anaerobic conditions.

Abstract-Coded caching is a recently proposed technique for dealing with large scale content distribution over the Internet. As in conventional caching, it leverages the presence of local caches at the end users. However, it considers coding in the caches and/or coded transmission from the central server and demonstrates that huge savings in transmission rate are possible when the server and the end users are connected via a single shared link. In this work, we consider a more general topology where there is a layer of relay nodes between the server and the users, e.g., combination networks studied in network coding are an instance of these networks. We propose novel schemes for a class of such networks that satisfy a so-called resolvability property and demonstrate that the performance of our scheme is strictly better than previously proposed schemes.

Mixed transition-metal oxides have witnessed increasing attention in catalysts and electrocatalysts. Herein, reduced graphene oxide-wrapped ZnMn2O4 microspheres (ZnMn2O4@rGO) were facilely synthesized through the solvothermal technique. The microstructure and morphology of ZnMn2O4@rGO microspheres were analyzed under Raman, X-ray photoelectron, X-ray diffraction, and energy-dispersive spectroscopies and scanning electron microscopy. The synthesized ZnMn2O4@rGO was employed as an excellent electrocatalyst for the reduction of hydrogen peroxide (H2O2). The ZnMn2O4@rGO-modified glassy carbon electrode (ZnMn2O4@rGO/GCE) exhibited a linear detection to H2O2 in a wide concentration range of 0.03–6000 μM with a detection limit of 0.012 μM. The biosensor was evaluated to determine H2O2 secreted by human breast cancer cells (MCF-7), indicating its promising applications in physiology and diagnosis.

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Abstract-Caching is popular technique in content delivery networks that allows for reductions in transmission rates from the content-hosting server to the end users. Coded caching is a generalization of conventional caching that considers the possibility of coding in the caches and transmitting coded signals from the server. Prior results in this area demonstrate that huge reductions in transmission rates are possible and this makes coded caching an attractive option for the next generation of content-delivery networks. However, these results require that each file hosted in the server be partitioned into a large number (i.e., the subpacketization level) of non-overlapping subfiles. From a practical perspective, this is problematic as it means that prior schemes are only applicable when the size of the files is extremely large. In this work, we propose a novel coded caching scheme that enjoys a significantly lower subpacketization level than prior schemes, while only suffering a marginal increase in the transmission rate. In particular, for a fixed cache size, the scaling with the number of users is such that the increase in transmission rate is negligible, but the decrease in subpacketization level is exponential.

Coded computation is an emerging research area that leverages concepts from erasure coding to mitigate the effect of stragglers (slow nodes) in distributed computation clusters, especially for matrix computation problems. In this work, we present a class of distributed matrix-vector multiplication schemes that are based on codes in the Rosenbloom-Tsfasman metric and universally decodable matrices. Our schemes take into account the inherent computation order within a worker node. In particular, they allow us to effectively leverage partial computations performed by stragglers (a feature that many prior works lack). An additional main contribution of our work is a companion matrix-based embedding of these codes that allows us to obtain sparse and numerically stable schemes for the problem at hand. Experimental results confirm the effectiveness of our techniques.